Polymeric composition for seals and gaskets

ABSTRACT

The present invention relates to a polymeric composition which has an excellent combination of properties for use in making seals and gaskets for utilization in appliances, automotive applications, and building applications, such as window glazing gaskets. These polymeric compositions offer excellent dimensional stability, low compression set, outstanding sealing characteristics, low temperature flexibility, heat resistance and ultra-violet light resistance. The present invention more specifically discloses a polymeric composition having excellent characteristics for utilization in manufacturing seals and gaskets including dimensional stability, low compression set and outstanding sealing characteristics, said polymeric composition being comprised of a blend of (A) a thermoplastic resin selected from the group consisting of polypropylene, polyethylene, poly phenylene ether, polystyrene, and styrene containing copolymer resins, (B) an elastomeric polymer selected from the group consisting of block copolymer comprising a first polymeric block that is comprised of repeat units that are derived from a vinyl aromatic monomer and a second block that is comprised of repeat units that are derived from a conjugated diolefin monomer, wherein the repeat units in the second block are hydrogenated, and wherein the repeat units in the second block are elastomeric in nature, and a crosslinked olefinic elastomer, (C) a high molecular weight crosslinked diene elastomer comprised of repeat units that are derived from conjugated diene monomer selected from the group consisting of 1,3-butadiene and isoprene, wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 200,000, and (D) an oil.

This application claims the benefit of United States Provisional PatentApplication Ser. No. 60/544,504, filed on Feb. 13, 2004.

BACKGROUND OF THE INVENTION

Seals for utilization in appliances (such as, refrigerators, freezers,and ice makers), automotive body applications (such as, windows, hoods,trunks and doors), and building applications (such as window glazinggaskets and weather strips) should be dimensional stable, provide lowcompression set and offer outstanding sealing characteristics over abroad temperature range. In many applications it is important for theseals to be capable of sealing out noise, wind and water, whileproviding long-term ultraviolet light resistance. At the same time, thematerial used in the seal must offer the degree of flexibility requiredfor the particular application. Window and door weather stripping forautomobiles and trucks is a high volume application for such seals.However, seals offering essentially the same characteristics are alsoneeded for sun roof seals, handle gaskets, window spacers, windowguides, lock seals, windshield wiper pivot seals and in buildingapplications such as window glazing gaskets and weather seals. Gasketsutilized in plumbing applications and appliances must also be capable offorming a liquid/gas tight seal and low compression set.

Rubbery blends of polyvinyl chloride (PVC) with a nitrile rubber (NBR)have sometimes been used in seals for automotive body applications. Thenitrile rubber is included in such blends as a permanent modifier forthe PVC which provides it with a higher degree of flexibility. However,the utilization of standard nitrile rubber in such blends typicallyresults in only moderate compression set characteristics. It is veryimportant for seals to have good compression set characteristics in mostapplications. For instance, improved resistance to water leaks and windnoise can be attained by utilizing a seal which has low compression setcharacteristics.

It is known from the teachings of United Kingdom Patent Application No.9214969.9 that low compression set characteristics can be improved byutilizing a technique known as “dynamic vulcanization” via free radicalgenerators, such as azo compounds or organic peroxides. However, this“dynamic vulcanization” technique suffers from the weakness that the azocompounds or organic peroxides required reduce the thermal stability ofthe polyvinylchloride resin and the ultraviolet light resistance of thenitrile rubber. There is also an increased risk of early crosslinkingduring processing which leads to scorching and reduced recyclability.

U.S. Pat. No. 5,362,787 discloses a highly crosslinked nitrile rubberwhich can be easily blended with PVC to make compositions which have anexcellent combination of properties for use in making seals and gasketsfor automotive and building applications. The PVC blends made with suchhighly crosslinked nitrile rubbers offer excellent dispersion behavior,dimensional stability, low compression set, outstanding sealingcharacteristics, and low temperature flexibility.

U.S. Pat. No. 5,362,787 more specifically discloses a highly crosslinkednitrile rubber composition which can be blended with polyvinyl chlorideto make compositions having excellent characteristics for seals andgaskets including dimensional stability, low compression set,outstanding sealing characteristics and good low temperatureflexibility, said highly crosslinked nitrile rubber composition beingcomprised of (1) a highly crosslinked nitrile rubber having repeat unitswhich are derived from (a) 1,3-butadiene, (b) acrylonitrile and (c) acrosslinking agent, wherein said highly crosslinked nitrile rubber has aMooney viscosity of about 50 to about 120, a swelling index of less thanabout 10 percent, a mill shrinkage of less than 10 percent, and a gelcontent of greater than 90 percent; and (2) from about 1 to about 30 phrof a plasticizer.

U.S. Pat. No. 5,380,785, U.S. Pat. No. 5,415,940 and U.S. Pat. No.5,462,993 disclose a rubbery polymer which can be blended with polyvinylchloride to make leathery compositions having good heat and ultravioletlight resistance, said rubbery polymer being comprised of repeat unitswhich are comprised of (a) butyl acrylate, or optionally a mixture ofbutyl acrylate and 2-ethylhexyl acrylate containing up to about 40percent 2-ethylhexyl acrylate, (b) at least one member selected from thegroup consisting of methyl methacrylate, ethyl methacrylate, methylacrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e) a halfester maleate soap and (f) a crosslinking agent.

U.S. Pat. No. 5,927,029 discloses a polymeric composition havingexcellent characteristics for seals and gaskets including dimensionalstability, low compression set and outstanding sealing characteristics,said polymeric composition being comprised of a vulcanized blend of (1)a rubbery polymer which is comprised of repeat units which are derivedfrom (a) butyl acrylate, (b) at least one member selected from the groupconsisting of methyl methacrylate, ethyl methacrylate, methyl acrylate,and ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) acrosslinking agent; (2) a thermoplasticstyrene/ethylene-butylene/styrene resin; and (3) at least one glycolcomponent selected from the group consisting of ethylene glycol andtriethylene glycol.

SUMMARY OF THE INVENTION

The present invention relates to a polymeric composition which has anexcellent combination of properties for use in making seals and gasketsfor utilization in appliances, automotive applications, and buildingapplications, such as window glazing gaskets. These polymericcompositions offer excellent dimensional stability, low compression set,outstanding sealing characteristics, low temperature flexibility, heatresistance and ultra-violet light resistance.

The present invention more specifically discloses a polymericcomposition having excellent characteristics for utilization inmanufacturing seals and gaskets including dimensional stability, lowcompression set and outstanding sealing characteristics, said polymericcomposition being comprised of a blend of (A) a thermoplastic resinselected from the group consisting of polypropylene, polyethylene, polyphenylene ether, polystyrene, and styrene containing copolymer resins,(B) an elastomeric polymer selected from the group consisting of blockcopolymer comprising a first polymeric block that is comprised of repeatunits that are derived from a vinyl aromatic monomer and a second blockthat is comprised of repeat units that are derived from a conjugateddiolefin monomer, wherein the repeat units in the second block arehydrogenated, and wherein the repeat units in the second block areelastomeric in nature, and a crosslinked olefinic elastomer, (C) a highmolecular weight crosslinked diene elastomer comprised of repeat unitsthat are derived from conjugated diene monomer selected from the groupconsisting of 1,3-butadiene and isoprene, wherein the high molecularweight diene elastomer has a weight average molecular weight of at leastabout 200,000, and (D) an oil.

The present invention further reveals a process for making a polymericcomposition having excellent characteristics for seals and gasketsincluding dimensional stability, low compression set and outstandingsealing characteristics, said process comprising dynamically vulcanizinga blend of (A) a thermoplastic resin selected from the group consistingof polypropylene, polyethylene, poly phenylene ether, polystyrene, andstyrene containing copolymer resins, (B) an elastomeric polymer selectedfrom the group consisting of block copolymer comprising a firstpolymeric block that is comprised of repeat units that are derived froma vinyl aromatic monomer and a second block that is comprised of repeatunits that are derived from a conjugated diolefin monomer, wherein therepeat units in the second block are hydrogenated, and wherein therepeat units in the second block are elastomeric in nature, and acrosslinked olefinic elastomer, (C) a high molecular weight crosslinkeddiene elastomer comprised of repeat units that are derived fromconjugated diene monomer selected from the group consisting of1,3-butadiene and isoprene, wherein the high molecular weight dieneelastomer has a weight average molecular weight of at least about200,000, and (D) an oil.

The present invention also discloses a gasket which is comprised of adynamically vulcanized blend of (A) a thermoplastic resin selected fromthe group consisting of polypropylene, polyethylene, poly phenyleneether, polystyrene, and styrene containing copolymer resins, (B) anelastomeric polymer selected from the group consisting of blockcopolymer comprising a first polymeric block that is comprised of repeatunits that are derived from a vinyl aromatic monomer and a second blockthat is comprised of repeat units that are derived from a conjugateddiolefin monomer, wherein the repeat units in the second block arehydrogenated, and wherein the repeat units in the second block areelastomeric in nature, and a crosslinked olefinic elastomer, (C) a highmolecular weight crosslinked diene elastomer comprised of repeat unitsthat are derived from conjugated diene monomer selected from the groupconsisting of 1,3-butadiene and isoprene, wherein the high molecularweight diene elastomer has a weight average molecular weight of at leastabout 200,000, and (D) an oil.

DETAILED DESCRIPTION OF THE INVENTION

The thermoplastic resin is normally a polyolefin resin or polystyrene.The polyolefin resin can be polyethylene, isotactic polypropylene,syndiotactic polypropylene, polypropylene impact copolymers containingabout 1-7 percent by weight of ethylene, butene, hexene, or octene,polyolefin copolymers such as ethylene-butene, hexene, or octene,polybutene, reactor grade modified polypropylene, oxypolyolefin, ormetallocene polypropylene. Syndiotactic polypropylene resins may also beused. Isotactic polypropylene copolymers with ethylene, butene or hexenethat are prepared with traditional Ziegler-Natta catalyst are highlypreferred.

A reactor grade impact modified polypropylene can also be used. Apublication article in Modem Plastics Encyclopedia/89, mid October 1988Issue, Volume 65, Number 11, pages 86-92, describes several types ofpolypropylenes, which is incorporated herein as a reference for thetypes of polypropylenes that may be used in the blends of the saidinvention. Metallocene based polypropylene resins that may be producedby single-site technology can also generally be used. The polypropyleneproduced by methods described in “Metocene™, Precise Tailoring ofPolypropylene Resins Using Single-Site Technology, David Fischer,Presented at the SPE Automotive TPO Global Conference 2001, HyattRegency, Dearborn, Mich., Oct. 1-3, 2001, can also normally be used. Theteachings of this reference are incorporated herein by reference.

Reactor grade thermoplastic olefins (TPOs) as produced by BasellPolyolefins and as described in TPE 2003 Conference Proceedings, RAPRATechnology Limited, Brussels, Belgium, Sep. 16-17, 2003, page 73 mayalso be used as a resin when a lower modulus and low hardness soft gripis desired. The reactor grade polypropylene that contains olefin rubbermolecules as described in TPE TPOCON 2003, SPE Topical ConferenceProceedings, Sep. 22-24, 2003, Paper Titled “A New ReactorEthylene-Propylene Plastomer with Increased Flexibility and LowerStiffnless”, Todd Glogovsky, Basell may also be used in this inventionand is incorporated herein as a reference. A linear low-densitypolyethylene resin may also be used for lower shore A hardness TPEcompounds.

Syndiotactic polypropylenes that are described in U.S. Pat. No.5,476,914 and U.S. Pat. No. 5,334,677 may be used in preparing thethermoplastic elastomer compositions. The teachings of U.S. Pat. No.5,476,914 and U.S. Pat. No. 5,334,677 are incorporated herein byreference. The syndiotactic polypropylenes used may be homopolymers orcopolymers. The syndiotactic polypropylenes utilized in the presentinvention comprise at least 15 percent syndiotactic molecules, morepreferably at least 50 percent syndiotactic molecules, and mostpreferably at least 82% syndiotactic molecules. Syndiotactichomopolymers or copolymers with ethylene may be used. For instance,commercial syndiotactic polypropylenes, such as those sold by Atofinamay be used. The syndiotactic polypropylene used will preferably have amelt flow rate greater than 0.5 g/10 minutes at 230° C./2.16 kg load asdetermined by ASTM D 1238, more preferably between 10 and 110 g/10minutes.

A reactor grade impact modified polypropylene can also be used. Apublication article in Modem Plastics Encyclopedia/89, mid October 1988Issue, Volume 65, Number 11, pages 86-92, describes several types ofpolypropylenes, which is incorporated herein as a reference for thetypes of polypropylenes that may be used in the blends of the saidinvention. Metallocene based polypropylene resins that may be producedby single-site technology can also generally be used. The polypropyleneproduced by methods described in “Metocene™, Precise Tailoring ofPolypropylene Resins Using Single-Site Technology, David Fischer,Presented at the SPE Automotive TPO Global Conference 2001, HyattRegency, Dearborn, Mich., Oct. 1-3, 2001, can also normally be used. Theteachings of this reference are incorporated herein by reference.

Reactor grade thermoplastic olefins (TPOs) as produced by BasellPolyolefins and as described in TPE 2003 Conference Proceedings, RAPRATechnology Limited, Brussels, Belgium, Sep. 16-17, 2003, page 73 mayalso be used as a thermoplastic resin, and teachings of which areincorporated herein as a reference.

The thermoplastic resins that are useful in the present invention alsoinclude polyphenylene ether (PPE) resins (also known within the art as“Polyphenylene Oxide), styrene containing copolymer resins such asstyrene-acrylonitrile resins (SAN), acrylonitrile-butadiene resins(ABS), and the functionalized versions of PPE and styrene containingresins that contain one functional group selected from the groupconsisting of maleic anhydride, hydroxyls, amines, epoxides, andglycidyl methacrylates.

The functional groups are particularly useful for compatibilizing thethermoplastic resins with the saturated block copolymers and the dienecontaining elastomers by virtue of reactive grafting of the functionalgroups present on the said thermoplastic resins with the functionalgroups present on the saturated block copolymers and the dienecontaining elastomers.

Polyphenylene ether resins that are most useful in this inventioninclude but are not limited to poly(2,6-dimethyl-1,4-phenylene ether),poly (2,6-dimethyl-co-2,3,6-trimethyl-1,4-phenylene ether), poly(2,3,6-trimethyl-1,4-phenylene ether), poly (2,6-diethyl-1,4-phenyleneether), poly (2-methyl-6-propyl-1,4-phenylene ether),poly(2,6-dipropyl-1,4-phenylene ether),poly(2-ethyl-6-propyl-1,4-phenylene ether), poly(2,6-dilauryl-1,4-phenylene ether), poly(2,6-dephenyl-1,4-phenyleneether), poly(2,6-dimethoxy-1,4 phenylene ether), poly(1,6-diethoxy-1,4-phenylene ether),poly(2-methoxy-6-ethoxy-1,4-phenylene ether),poly(2-ethyl-6-stearyloxy-1,4-phenylene ether),poly(2,6-dichloro-1,4-phenylene ether),poly(2-methyl-6-phenyl-1,4-phenylene ether), poly(2-ethoxy-1,4-phenyleneether), poly(2-chloro-1,4-phenylene ether),poly(2,6-dibromo-1,4-phenylene ether), andpoly(3-bromo-2,6-dimethyl-1,4-phenylene ether), their respectivehomopolymers or copolymers.

Block copolymers consisting of at least two polymeric blocks (A)composed mainly of a vinyl aromatic compound and at least one polymericrubbery block (B) composed mainly of hydrogenated compounds or unitsthat are obtained by the hydrogenation of conjugated diene compound, areto be used in this invention. It is preferred that in the blockcopolymer, a minimum number of two blocks are present, one composed of avinyl aromatic compound or units such as styrene that provides stiffnessor reinforcement, and another that is composed mainly of hydrogenatedcompounds or units that are obtained by the substantial hydrogenation ofthe conjugated diene compound or units, and provides elasticity. It ishighly preferred that the block copolymer is a triblock copolymer withtwo end blocks of a vinyl aromatic compound and a rubbery mid block ofsubstantial number of hydrogenated compounds or units. Block copolymerswith partially hydrogenated mid-blocks may also be used and may containa combination of hydrogenated compounds or units and their pre-cursordiene compounds or units. The block copolymers that may be used in thisinvention are selected from the group ofstyrene-ethylene,butylenes-styrene (SEBS), styrene-ethylene,propylene-styrene (SEPS), hydrogenated styrene-isoprene copolymer,styrene-ethylene propylene (SEP) block copolymer,styrene-ethylene,ethylene propylene-styrene (SEEPS) and hydrogenatedstyrene-butadiene copolymer. Hydrogenated products that are copolymersor homopolymers of isoprene and butadiene-containing monomer units mayalso be used. The hydrogenation of random diene copolymers are describedby authors E. W. Duck, J. R. Hawkins, and J. M. Locke, in Journal of theIRI, 6, 19, 1972, which may be used as the highly saturated elastomer inthis invention and is incorporated herein as a reference. The saturatedtriblock polymers, SEBS and SEPS, with styrene end blocks are also usedin this invention as the saturated elastomers. SEBS and SEPS areobtained on the hydrogenation of triblock copolymers of styrene andbutadiene or styrene and isoprene and are known to be commerciallyavailable. Some commercial available examples of such elastomers includeKraton® G series polymers. U.S. Pat. No. 3,686,364 and U.S. Pat. No.3,865,776 give some examples of block copolymers that may be used in thepractice of this invention and are incorporated herein by reference. Itis highly preferred that the highly saturated elastomer to be SEBShaving a bound styrene content that is within the range of 15 weightpercent to about 40 weight percent.

It is possible to use the saturated block copolymers that are modifiedversions of SEBS. Such modified block copolymers additionally have asubstantial number of styrene units that are randomly distributed in therubber midblocks of ethylene and butylene. These modified saturatedblock copolymers are supplied under Kraton® ‘A’ series. Saturated blockcopolymers grades as mentioned in TPE 2003 RAPRA Conference Proceedings,Brussels, Belgium, Sep. 16-17, 2003, Paper 18, Page 157, and Paper 21,page 181 may also be used and are incorporated herein by reference.

Hydrogenated diblock elastomers of styrene and butadiene or styrene andisoprene can also be used as the block copolymers or saturated blockcopolymers even though triblock elastomers are highly preferred. Theblock copolymers as used in this invention will be substantiallysaturated or hydrogenated. It is preferred that at least 75 percent ofthe original double bonds of the isoprene and/or butadiene units thatare present in the block copolymers prior to the hydrogenation have beensaturated by the hydrogenation process, more preferably at least 90percent and most preferably at least 95 percent of the original doublebonds have been saturated. Block copolymers that are partiallyhydrogenated may also be used, even though highly hydrogenated orsaturated block copolymers are highly preferred.

The block copolymers that are useful in this invention are generallydescribed in Chapter 11, Thermoplastic Elastomers, 2^(nd) Edition,Hanser Publishers, 1996, which is incorporated herein by reference.

The block copolymer will preferably be of a high molecular weight, withthe weight average molecular weight greater than 200,000 grams/mole,more preferably greater than 275,000 grams/mole, and most preferablythat is greater than 375,000 grams/mole. The block copolymer willpreferably be oil extended with about 15 to about 600 parts of oil ofthe said block copolymer. It is also possible to add the oil in part orfull during the thermo-mechanical mixing and the dynamic vulcanizationof the said crosslinkable elastomer. The oil will preferably be aparaffinic, napthenic or polybutene. The triblock copolymer may beobtained by the hydrogenation of the diene units or compounds that havea higher vinyl content of no less than 30% of the said diene units orcompounds. The thermoplastic resin will typically be present at a levelwhich is within the range of about 5 parts by weight to 60 parts byweight, the elastomeric polymer will typically be present at a levelwhich is within the range of 5 parts by weight to about 90 parts byweight, the high molecular weight crosslinked diene elastomer willtypically be present at a level which is within the range of about 5parts by weight to about 90 parts by weight, and the oil will typicallybe present at a level which is within the range of about 15 parts byweight to about 600 parts by weight.

In this specification, the term vulcanization or crosslinking or curingcan be used interchangeably and indicate that the molecules of a polymerare linked together or are linked with the molecules of another polymer.

In this specification, the term elastomer and rubber are usedinterchangeably. The term thermoplastic elastomer refers to a polymericmaterial that has elastomer like properties and has thermoplasticprocessability and recyclability.

For purposes herein, the term elastomer and rubber indicate that thepolymeric material exhibits a combination of high elongation orextensibility, high retractability to its original shape or dimensionsafter removal of the stress or load, with little or no plasticdeformation and possesses low modulus and requires a low load to stretchthe material. The term thermoplastic resin means a material havingthermoplastic processability and has a high modulus and stiffness.Thermoplastic resins do not exhibit a combination of high elongation orextensibility, and are not retractable to their original shape ordimensions particularly when stretched and released beyond their yieldpoint. High loads are required to stretch thermoplastic resins. Rubberelasticity is defined in Chapter 3 of L.R.G. Treloar, Introduction toPolymer Science (Wyneham Publications (London) Ltd. 1974), the teachingsof which are incorporated herein by reference.

In this specification, the diene containing crosslinked elastomer is anelastomer that is comprised of repeat units that are derived fromconjugated diene monomers selected from the group consisting of1,3-butadiene and isoprene, and the elastomer has been crosslinkedduring the thermomechanical mixing step.

In this specification, the crosslinked olefin elastomer is an elastomerthat is comprised of olefin units, and has been crosslinked during thethermomechanical step. The crosslinked olefin elastomer will haveolefinic segments and will not have blocks that are derived from a vinylaromatic monomer. The crosslinked olefin elastomer may be a copolymerprepared by the copolymerization of olefins and a diene containingmonomer, particularly a non-conjugated diene monomer, and the weightpercent of the diene in the olefin elastomer will be less than about 15%by weight of the said elastomer.

The crosslinking of the olefin and diene containing elastomer will becarried-out during the thermo-mechanical mixing step and in the presenceof a thermoplastic resin. The crosslinking of the olefin and dieneelastomer may be carried-out either separately or simultaneously.

The diene elastomer will be of a high weight average molecular weight.The weight average molecular weight will preferably be greater thanabout 200,000 g/mole, and more preferably be greater than and about275,000 g/mole, and most preferably be greater than and about 350,000g/mole. It is very important for the diene elastomer to have a highweight average molecular weight.

The crosslinked diene elastomer polymerized by solution polymerizationtechniques can be a diene elastomer that is made with polymerization ina solvent such as hexane or cyclohexane. Such elastomers are well knownto those skilled in this art. U.S. Pat. No. 6,566,478, U.S. Pat. No.6,313,216, U.S. Pat. No. 6,372,863, U.S. Pat. No. 6,293,325, U.S. Pat.No. 6,289,959, U.S. Pat. No. 6,140,434, U.S. Pat. No. 5,844,044, U.S.Pat. No. 5,679,751,U.S. Pat. No. 5,677,402, U.S. Pat. No. 5,448,003,U.S. Pat. No. 5,239,009 and U.S. Pat. No. 5,272,220 generally describesuch elastomers and methods for their synthesis. The teachings of theseUnited States patents are incorporated herein by reference with respectto their description of such elastomers and their synthesis. Theelastomers used will be substantially random. Solution elastomers suchas synthetic-polyisoprene may also be used. The solution elastomers usedmay be styrene-butadiene random copolymer or styrene-isoprene randomcopolymer with about 10 to about 40% by weight of bound styrene content.The Mooney viscosity of the said solution elastomer may be in the rangeof about 15 to about 120 Mooney as measured per ML 1+4 at 100° C. Thestyrene butadiene rubber will preferably have a vinyl content which iswithin the range of about 10 to 80%.

The solution diene rubbers that are particularly more useful in thisinvention for use as crosslinkable elastomers are the modified orcoupled elastomers such as copolymers of styrene and diene selected frombutadiene and isoprene and the living polymer, before terminating thepolymerization, modified with tin or silicon. Such modified elastomersmay also be for example styrene/butadiene copolymers andstyrene/isoprene/butadiene ter-polymers. Homopolymers of diene may alsobe employed, but it is more preferred to have the styrene be present asa co-monomer. Copolymers of Isoprene and butadiene may also be used.

The dynamically crosslinked diene elastomer may be comprised of monomerunits that are derived from 1,3-butadiene and isoprene, and a vinylaromatic monomer, wherein the monomer units are essentially distributedin a random manner.

An important characteristics of the diene coupled elastomer,particularly the tin-modified elastomers, is that a substantial portion,preferably at least 40%, and more generally in the range of about 60 toabout 85% of the tin (Sn) bonds or silicon (Si) bonds are bonded to thediene units of the styrene/diene copolymer, which may be referred hereinas tin-dienyl or silicon-dienyl bond, for example butadienyl bonds incase of butadiene terminating with the tin (or silicon).

A copolymer-coupled elastomer may be prepared by copolymerization ofstyrene with 1,3-butadiene and/or isoprene in an organic solution withan alkyl lithium catalyst. A co-catalyst or catalyst modifier may alsobe used. Such polymerization methods are well known to those skilled inthis art. After formation of the copolymer elastomer, but while thecatalyst is still active and, therefore, while the copolymer is stillconsidered a living or live polymer that is capable of furtherpolymerization, the polymerization can be terminated by reacting thelive polymer with a tin or silicon compound such as tin tetrachloride.This taking into account that the valence of tin is four, typically themodified copolymer is considered coupled or capped, with an accompanyingmolecular weight or viscosity jump or increase, and the modifiedcopolymer being in what is sometimes called as a star shaped, or starconfigured, coupled elastomer.

Coupling compounds similar to tin tetrachloride with a lower or highervalence may also be used to obtain an architecture that is higher orlower in the average number of arms that are obtained from a tintetrachloride that has a valence of four. A tin coupled copolymerelastomer can also be obtained via coupling with an organo tin compoundsuch as for example alkyl tin chloride, dialkyl tin chloride, andtrialkyl tin chloride, resulting in variations in the tin coupledpolymer with the tin chloride yielding simply a tin terminatedcopolymer.

A coupled styrene/isoprene/butadiene terpolymer. Some examples ofpreparation of such coupled elastomers is further given in followingJournal Articles: “Solution-Polymerized Rubbers with Superior BreakdownProperties” Journal of Applied Polymer Science Vol. 14, PP 1421-1432(1970), “Tin Coupled SBRs: Relationship between Coupling Type andProperties, Paper No 78, Presented at 148^(th) Meeting of the RubberDivision, American Chemical Society, Cleveland, Ohio, Oct. 17-20, 1995,and “Newly Developed Solution SBRs for Low Rolling Resistance Tire”, RCT1990 V 63 #1, P 8-22, which are incorporated herein as a reference.

Some examples of modified or coupled solution elastomers such as tin orsilicon-coupled, with several variations are given in U.S. Pat No.6,090,880, U.S. Pat. No. 5,064,910, U.S. Pat. No. 4,553,578, U.S. Pat.No. 4,444,236, U.S. Pat. No. 5,362,794, U.S. Pat. No. 5,677,399, U.S.Pat. No. 5,786,441, U.S. Pat. No. 6,008,295, U.S. Pat. No. 6,252,007,and U.S. Pat. No. 6,228,908, which are incorporated herein as areference, as they may also be used in thermoplastic elastomers asdisclosed in this invention.

It may also be preferred to use the random copolymers of styrene,butadiene, and isoprene or copolymers of isoprene and butadiene that areprepared with solution polymerization techniques. Such rubbery andunsaturated copolymers may be highly branched with varying vinyl contentfrom about 5 to about 80 percent. The copolymers may be coupled with Sn(SiCl4) or Si (SiCl4) coupling and may have multiple arms or branches.

The crosslinked diene elastomer can also be a nitrile rubber or itshydrogenated version (hydrogenated nitrile rubber), and theacrylonitrile content may vary from about 5 to about 60% by weight ofthe said elastomer and may be as high to allow the polymer to exhibit anelastomer like extensibility and retractability. The nitrile rubber maybe substantially or partially hydrogenated. The diene units in thenitrile rubber may be hydrogenated from about 40% to about 98% byweight. Such hydrogenated elastomers are commercially available fromZeon Chemicals. It may be necessary to use a compatibilizer tocompatibilize the polar nitrile or hydrogenated nitrile rubber with therelatively non-polar block copolymer. The compatibilizer may consist ofa combination of polar and non-polar segments. It is preferred that thecompatibilizer is elastomeric in nature so that it has highextensibility and retractability. A polyamide-block-ether elastomer maybe used to compatibilize the nitrile rubber or its hydrogenatedderivative with the block copolymer.

The diene elastomer may be a functionalized elastomer that hasfunctional groups that are grafted or copolymerized on the elastomer andthe said functional groups are selected from the group consisting ofepoxide, carboxylic acid or anhhydride, glycidyl methacrylate, hydroxyl,and amine. The functionalized elastomer is particularly useful forcompatibilizing the more polar thermoplastic resins with the relativelynon-polar block copolymers.

Crosslinked diene elastomer may also be prepared by emulsionpolymerization techniques wherein the polymerization is carried out inan aqueous medium. However, the diene elastomers synthesized by solutionpolymerization techniques are highly preferred.

Olefin elastomer useful to prepare thermoplastic elastomers according tothe invention include monoolefin copolymer rubbers comprising non-polar,rubbery copolymers of two or more monoolefins (EPR rubber), preferablycopolymerized with at least one polyene, usually a diene (EPDM rubber).EPDM is a polymer of ethylene, propylene and one or more non-conjugateddiene(s), and the monomer components may be polymerized usingZiegler-Natta or metallocene catalyzed reactions, among others.Typically an EPDM rubber has from about 0.5 to about 6 or 10 weightpercent of a diene (based on the weight of the polymer) and has a molarratio of repeat units from ethylene to propylene of from 25:75 to 75:25.Satisfactory non-conjugated dienes include 5-ethylidene-2-norbornene(ENB); 1,4-hexadiene (HD); 5-methylene-2-norbomene (MNB); 1,6-octadiene;5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene;1,4-cyclohexadiene; dicyclopentadiene (DCPD); 5-vinyl-2-norbornene (VNB)and the like, or a combination thereof.

U.S. Pat. No. 6,150,464 lists the types of EPDM elastomers and thehydrosilation crosslinking agents that may be used in this invention,and is incorporated herein as a reference. It was reported in U.S. Pat.No. 6,150,464 in that rubber having a structure in which the dienemonomer has carbon-carbon multiple bonds which are predominantlyunencumbered, i.e. bonds which are sterically unhindered such asterminal or pendant double bonds, provide a greatly improved rate ofcure in the hydrosilylation curing process of the invention.

The use of saturated olefinic rubber in which the diene component isselected from the group consisting of 5-ethylidene-2-norbornene,5-methyl-1,4-hexadiene, 1,4-hexadiene and 5-vinyl-2-norbomene ispreferred. A structure from 5-vinyl-2-norbomene is particularlypreferred as a diene component of such rubber. Highly branched forms ofolefinic elastomers may also be used.

Olefin elastomers that are used to prepare thermoplastic vulcanizatesare also described in U.S. Pat. Nos. 5,750,625 and 4,130,535 which areincorporated herein by reference for the type of olefinic elastomers andtheir crosslinking technologies that may be used in this invention tocrosslink the elastomers.

The thermoplastic elastomer blend composition useful for the preparationof the sealing article will comprise of a processing oil. Examples ofsuch oils that can be used include Paralux™ process oils 701R, 1001R,2401R, 6001R, from Chevron and the like. It is preferred to use an oilwith a high flash point for better retention of the oil. Naphthenic oilsare preferred with for use in blends having a relatively high styrenecontent and paraffinic oils are preferred for utilization in conjunctionwith blends having a relatively low styrene content.

U.S. Pat. No. 6,251,998, U.S. Pat. No. 6,169,145, U.S. Pat. No.6,150,464, U.S. Pat. No. 6,147,160, U.S. Pat. No. 6,084,031, U.S. Pat.No. 5,672,660, U.S. Pat. No. 5,936,028, and U.S. Pat. No. 4,803,244teach the methods and hydrosilation crosslinking systems for dynamicvulcanization of the diene elastomers and/or olefin elastomer inpresence of a hard and non-rubbery thermoplastic resin, and areincorporated herein as a reference. The thermoplastic elastomercontaining a diene containing crosslinkable elastomer will preferably becrosslinked with a hydrosilation or hydrosilylation system wherein thehydrosilation catalyst is selected from the group consisting of aplatinum, platinum zero compounds complexed with compounds selected fromcarbon monoxide, fumarates, phosphines, divinyltetramethyldisiloxanes,tetravinyldimethyldisiloxanes, palladium, chloroplatinic acid, platinumchloride complexes in alcohols, and rhodium, that is complexed with amember selected from polyvinyltetramethyldisiloxanes orcyclovinylmethylsiloxanes wherein additional divinylsiloxanes orpolyvinylmethylcyclosiloxanes are present, wherein the catalyst orcatalyst complexed compounds are incorporated on the block copolymer,crosslinkable elastomer, and/or oil, and are preferably present fromabout 0.0015 to about 1 parts metal catalyst by weight of thecrosslinkable elastomer. The hydrosilation agent will most preferably betetrakis (dimethylhydrogensiloxy)silane ortetrakis(dimethylsiloxy)silane. The hydrosilation catalyst will mostpreferably be a platinum zero compound that is complexed with carbonmonoxide and polyvinylmethylcyclicsiloxanes to give a platinum carbonylcomplex in cyclic methylvinylsiloxanes.

The preparation of the thermoplastic elastomer (also called as TPE)composition may be carried out in a continuous mixer, or a combinationof a continuous mixer and a batch mixer. When a batch mixer is used, thedischarged and uncrosslinked blend may be fed through a singlescrew-extruder and pelletized. When a continuous mixer is used, theblend may be pelletized after discharging from the twin-screw extruder.The dynamic vulcanization of the unsaturated diene elastomer or rubberypolymer or elastomer will be preferably carried out in a continuousmixer such as a twin-screw extruder or a Farrel continuous mixer. Afterthe preparation of the thermoplastic elastomer composition, theelastomer may be extruded, thermoformed, or injection molded to form thesealing article.

The seal can be a weatherseal as described in U.S. Pat. No. 6,368,700 orU.S. Pat. No. 4,616,445, the teachings of which are incorporated hereinby reference. The seal can also be in the form of a gasket having anO-ring design meeting the specifications provided by ASTM DesignationF477-99 or D3212-96a. The thermoplastic elastomer blend can also be usedin manufacturing adjustable entrance seals as described in U.S. Pat. No.5,704,656, the teachings of which are incorporated herein by reference.The thermoplastic elastomer blends of this invention can also be used asa replacement for cork and can be used as a sealing material insynthetic closures, such as a stopper for wine bottles.

The thermoplastic elastomer blend composition may also containreinforcement or fillers selected from the group consisting of talc,clay, calcium carbonate, silica, carbon black, and wollastonite. Thethermoplastic elastomer blends may also contain antiozonants andoxidants that are known to a rubber chemist of ordinary skill. Theantiozonants may be physical protectants such as waxy materials thatcome to the surface and protect the part from oxygen or ozone or theymay chemical protectors. The chemical protectors may be selected fromthe class of styrenated phenols, butylated octylated phenol, butylateddi(dimethylbenzyl) phenol, p-phenylenediamines, butylated reactionproducts of p-cresol and Dicyclopentadiene (DCPD, polyphenolicanitioxidants, hydroquinone derivatives, quinoline, diphenyleneantioxidants and thioester antioxidants and the like and their blends.Some representative trade names of suitable products include Wingstay® Santioxidant, Wingstay® T antioxidant, Polystay® C antioxidant, Polystay®100 antioxidant, Polystay® 100 AZ antioxidant, Polystay® 200antioxidant, Wingstay® L antioxidant, Wingstay® LHLS antioxidant,Polystay® K antioxidant, Polystay® 29 antioxidant, and Wingstay® SN-1.The antioxidants and antiozonants used will preferably be non-stainingand non-migratory. For applications that require non-black pigmentationor compositions where the natural color may be desired, carbon black maynot be used and above mentioned antioxidants and antiozonant may be usedinstead. It is important that the said elastomer contains a significantportion of the antioxidant and antiozonant and/or carbon black (wheneverused) in the said blends.

The uncoupled solution polymerized diene elastomers used in blends withthe highly saturated and olefin elastomers will have a vinyl contentbetween 10 and 70 percent by weight, more particularly between 20 and 55percent by weight. The uncoupled solution elastomers may be furthercomprised of a vinyl aromatic monomer selected from the group consistingof styrene and alpha-methylstyrene with the bound content of the vinylaromatic monomer in the range of about 10 to about 50 percent by weight.

For providing additional stability against UV radiation, hindered aminelight stabilizers (HALS) and UV absorbers may be also used in thethermoplastic elastomer composition. A skilled person is aware of suchstabilizers. For example, Tinuvin® RTM 123, 144, 622, 765, 770 and 780,and Chemisorb® TTM-944 and the like may be employed. These kinds of UVstabilizers are available from Ciba Specialty Chemicals and CytexIndustries.

When the diene and/or olefin elastomer is fully or partially cured inthe thermoplastic elastomer compositions, curatives of the known art maybe employed. The curing may be accomplished by dynamic vulcanization,wherein the rubber phase is generally crosslinked simultaneously as itis being mixed with the thermoplastic resin. The curatives may beselected from sulfur based, peroxide based, or phenolic based curatives.U.S. Pat. No. 3,758,643, U.S. Pat. No. 3,806,558, U.S. Pat. No.5,051,478, U.S. Pat. No. 4,104,210, U.S. Pat. No. 4,130,535, U.S. Pat.No. 4,202,801, U.S. Pat. No. 4,271,049, U.S. Pat. No. 4,340,684, U.S.Pat. No. 4,250,273 U.S. Pat. No. 4,927,882, U.S. Pat. No. 4,311,628 andU.S. Pat. No. 5,248,729 teach the type of curing or crosslinking agentsand methods that can be utilized and the teaching of these referencesare incorporated herein by reference.

When sulfur based curing agents are employed for curing the dienecontaining solution elastomer, accelerators and cure activators may beused. Accelerators are used to control the time and/or temperaturerequired for dynamic vulcanization and to improve the properties of thethermoplastic composition. In one embodiment, a single acceleratorsystem may be used, i.e., primary accelerator. The primaryaccelerator(s) may be used in total amounts ranging from about 0.5 toabout 4, preferably about 0.8 to about 1.5 phr (parts by weight perhundred parts by weight of rubber). In another embodiment, combinationsof a primary and a secondary accelerator might be used with thesecondary accelerator being used in smaller amounts, such as from about0.05 to about 3 phr, in order to activate and to improve the propertiesof the thermoplastic elastomer composition. Combinations of theseaccelerators might be expected to produce a synergistic effect on thefinal properties and are somewhat better than those produced by use ofeither accelerator alone. In addition, delayed action accelerators maybe used which are not affected by normal processing temperatures butproduce a satisfactory cure at ordinary vulcanization temperatures.Vulcanization retarders might also be used. Suitable types ofaccelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. Preferably, the primary accelerator is asulfenamide. If a second accelerator is used, the secondary acceleratoris preferably a guanidine, dithiocarbamate or thiuram compound. Certainprocessing aids and cure activators such as stearic acid and zinc oxide(ZnO) may also be used. When peroxide based curing agents are used,co-activators or coagents that are known to a rubber chemist of ordinaryskill may be used in combination with the peroxides. These coagents mayinclude trimethylolpropane triacrylate (TMPTA), trimethylolpropanetrimethacrylate (TMPTMA), triallyl cyanurate (TAC), triallylisocyanurate (TAIC), and the like. The peroxide crosslinkers and thecoagents that may be employed for partial or complete dynamicvulcanization can be selected from the journal publication, “PeroxideVulcanization of Elastomer”, Vol. 74, No 3, July-August 2001, theteachings of which are incorporated here by reference. Hydrosilationcrosslinking may also be employed to crosslink the diene-containingrubbery elastomer.

When the diene containing elastomer is at least partially crosslinked,the degree of crosslinking may be measured by dissolution of the blendin a solvent for specified duration, and using certain calculations tocompensate for the insoluble or resin portion and then calculate percentgel or unextractable rubber. The percent gel would normally increasewith increasing crosslinking level. These techniques are well definedand established and are known to the persons that are skilled in thisart. The percent gel content in the thermoplastic blends, more so in thethermoplastic vulcanizates (i.e. a thermoplastic elastomer withdynamically crosslinked elastomer) or TPVs may be anywhere in the rangeof about 5% to 100%.

When styrene-ethylene butylene-styrene (SEBS) triblock copolymers areused with the coupled diene elastomers, the weight average molecularweight of the SEBS as measured in size exclusion chromatography willpreferably be greater than 100,000 g/mole, more particularly greaterthan 150,000 g/mole, and most preferably greater than 300,000 g/mole.Higher molecular weight is desired for achieving better sealingperformance as measured by a low compression set and a higher retentionof sealing force with time.

When the highly saturated elastomer is an olefinic elastomer for usewith the uncoupled diene elastomer containing thermoplastic elastomercompositions, the olefinic elastomer may be selected from the groupconsisting of ethylene propylene diene rubber (EPDM), ethylene propylenecopolymer rubber (EPR), ethylene-octene copolymer rubber,ethylene-hexene copolymer rubber, and the like. The olefinic elastomermay be crosslinked with either peroxide, phenolic, or hydrosilationcuring or crosslinking systems. When the olefinic elastomer containssome diene units such as in EPDM, the phenolic or hydrosilationcrosslinking may be employed. When there is no unsaturation present inthe olefinic elastomer, peroxide crosslinking may be used. Suchcrosslinking technologies are known to those who are skilled in thisart. The EPDM elastomer can be synthesized by solution polymerization orgas phase technologies. Metallocene catalyst systems may also be used.The olefic elastomer will preferably have a Mooney ML 1+4 viscosity at125° C. that is greater than about 45.

Unsaturated rubbers useful to prepare thermoplastic elastomers accordingto the invention include monoolefin copolymer rubbers comprisingnon-polar, rubbery copolymers of two or more monoolefins (EPR rubber),preferably copolymerized with at least one polyene, usually a diene(EPDM rubber). EPDM is a polymer of ethylene, propylene and one or morenon-conjugated diene(s), and the monomer components may be polymerizedusing Ziegler-Natta or metallocene catalyzed reactions, among others.Typically an EPDM rubber has from about 0.5 to about 6 or 10 weightpercent of a diene (based on the weight of the polymer) and has a molarratio of repeat units from ethylene to propylene of from 25:75 to 75:25.The olefinic elastomer to be used in the compositions with the dienesolution elastomer may be available in a commercially availablethermoplastic vulcanizate sold by Advanced Elastomer Systems or DSM orA. Schulman or the olefinic elastomer may be crosslinked simultaneouslyalong with the uncoupled diene solution elastomer, in the presence ofthermoplastic resin and oils.

This invention is illustrated by the following examples that are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

Table 1 lists the characterization of the solution SBRs that were usedto prepare the masterbatch compositions that were subsequently used forpreparing thermoplastic elastomers that are useful in sealingapplications.

TABLE 1 Characterization of Solution SBR Used in Making Crosslinked SBRMasterbatch SBR1 SBR2 SBR3 SBR 4 % Bound Styrene 16 25.3 24.8 24.8 %Vinyl Content 42 51 14 14 Polymer Coupling SnCl₄ — — — Base MooneyViscosity 40 55 103 52 Final Mooney Viscosity 76 55 103 52 Base Mw(g/mole) 255,000 342,000 558,000 272,000 Coupled Mw (g/mole) 420,000 — —— Tg (° C.) Midpoint −41 −10 −56 −56

The SBR 1 is a coupled polymer that has been coupled with SnCL₄ duringthe polymerization process. SBR 3 and 4 are uncoupled polymers withdifferences in molecular weight. The weight average molecular weights(Mw) were measured by using Size Exclusion Chromatography andpolystyrene standards were used for calibration.

In case of the coupled SBR, the molecular weight prior to coupling (basemolecular weight) and after coupling (coupled molecular weight) weremeasured and are reported. Likewise, the Mooney Viscosity ML 1+4 @ 100°C. was also measured before and after coupling for the coupled SBR, andare reported above. Glass Transition temperatures (T_(g)) were measuredby Differential Scanning Calorimetry at heating rates of 10° C./minute.

Table 2 gives the composition of SBR masterbatches where SBR wasdynamically vulcanized in a twin-screw extruder in presence ofpolypropylene resin and above and about the melting point ofpolypropylene. Dynamic vulcanization of the SBR was carried-out in a 25mm co-rotating twin-screw extruder. Barrel temperatures of 180° C., anda screw speed of 300 RPM was employed in the extruder.

TABLE 2 Composition in % of Crosslinked SBR Masterbatches Made byDynamic Vulcanization No 1 2 3 4 SBR 1 59.35 — — — SBR 2 — 59.35 — — SBR3 — — 59.35 — SBR 4 — — — 59.35 Trigonox 101-45B-pd^(a)) 0.92 0.92 0.920.92 Talc^(b)) 7.77 7.77 7.77 7.77 Polypropylene^(c)) 31.96 31.96 31.9631.96 Total 100 100 100 100 ^(a))Peroxide crosslinking agent from AkzoNobel ^(b))Mistron Vapor R talc from Luzenac ^(c))Isotactic homopolymergrade 3825, Melt Flow Rate 30 g/10 minutes @ 230° C./2.16 Kg, suppliedby Atofina

Table 3 lists the compositions of oil extended TPE formulations.Crosslinked SBR masterbatch of Examples 1, 2, 3, and 4 (herein calledXL-SBR1, XL-SBR2, XL-SBR3 and XL-SBR4 respectively) were used and dryblended with an SEBS, Oil, and polypropylene copolymer containingconcentrate to form compositions of Examples 6, 7, 8, and 9respectively. The dry blends were molded by using a Battenfeld injectionmolding machine BA 800/315. The temperatures of 210/204/204/191° C. wereused for the Nozzle/Forward/Middle/Rear zones to mold the testspecimens. The composition of Example 5 (control) was prepared byseparate additions of the individual components in a Coperion ZSK25 twinscrew extruder with 8 barrels and 32 L/D. The throughput rate of 20lb/hour, barrel temperatures of 180° C., and a screw speed of 300 RPMwere employed. The compositions were injection molded as describedabove, and were tested for the physical properties.

TABLE 3 Oil Extended Soft TPE Compositions of SEBS and Crosslinked SBRMasterbatch Additions with SEBS No 5+ 6 7 8 9 XL-SBR 1 — 21.14 — — —XL-SBR 2 — — 21.14 — — XL-SBR 3 — — — 21.14 — XL-SBR 4 — — — — 21.14Kraton G 1651 60.41 39.27 39.27 39.27 39.27 Polypropylene 11.21 11.2111.21 11.21 11.21 (Atofina 3825, 30 MFI Isotactic Homopolymer)Polypropylene 10.69 10.69 10.69 10.69 10.69 (Atofina 7823 Mz IsotacticCopolymer 30 MFI) Renoil 471 14.96 14.96 14.96 14.96 14.96 Talc 2.732.73 2.73 2.73 2.73 Total 100 100 100 100 100 +Control

The physical properties of the thermoplastic elastomer compositions weretested generally in accordance with the relevant ASTM test methods;Durometer hardness D 2240-00, tensile properties D 412-98 a method A,tear strength D624-00, flexural properties D 790-00, compression setD395-01 method B, and effect of liquids D471-98.

TABLE 4 Properties of Oil Extended Soft TPE Compositions of SEBS andCrosslinked SBR Masterbatch Additions with SEBS No 5+ 6 7 8 9 Shore AHardness 85 84 83 83 84 Tensile Strength 17.4 11.5 12.2 10.2 11.2 (Mpa)Tear Strength 51.3 40 40.2 41.8 41 (N/mm) Flexural Modulus 57.7 50.546.2 48.6 47 (Mpa) % Compression Set B @ 23 C. 23.5 20.2 19.7 21.4 20.2@ 70 C. 67 43.5 41.3 43.7 43.5 % Weight Gain IRM Oil 903 67.5 50.3 49.253.8 56.6 @ 70 C. % Force Retention* Time t = 0 hours 100 100 100 100100 Time t = 250 hours 80 97 92 98 88 Time t = 500 hours 78 93 84 100 87+Control *Compressive Stress Relaxation, ISO 1183 test method, 23° C.,3.2 mm Ring Specimen Geometry, @ 25% Compression, % Force Retention =Force at Time t hours* 100/Force at Time 0 hours

The crosslinked SBR and oil extended SEBS containing thermoplasticelastomers have better compression set and oil resistance than the SEBScontrol 5. Low compression set is desired for sealing applications.Furthermore, the force retention in a stress relaxation experiment isthe very high for the TPE composition of Example 6 and Example 8 thatcontained crosslinked SBR1 (XL-SBR1) and crosslinked SBR 3 (XL-SBR3).Example 6 containing XL-SBR1 and Example 8 containing XL-SBR3 had veryhigh retention of sealing force that is believed to be attributed to avery high molecular weight of the styrene-butadiene rubber. Highretention of sealing force is also highly desirable for sealingapplications. SBR1 is a high vinyl content SBR that was coupled withSnCl₄. Coupled polymers with a high molecular weight and high vinylcontent provide excellent force retention in the a compressive stressrelaxation experiment. SBR 3 is a low vinyl uncoupled SBR with thehighest weight average molecular weight used. The TPE compositions ofExample 8 have the best force retention with no significant reduction inthe force retention values.

Better force retention may be further possible at higher proportions ofcrosslinked SBR in the blends with SEBS. Also, seals of lower shore Ahardness can be obtained by lowering the thermoplastic resin contentand/or increasing the oil content.

In the following examples, a commercially available thermoplasticvulcanizate that contains polypropylene, crosslinked EPDM and oil wasdry blended with each of masterbatches of crosslinked SBRs namelyXL-SBR1, XL-SBR3, and XL-SBR4. The crosslinked EPDM containingthermoplastic vulcanizate used was Santoprene® 201-55 of Shore A 55 fromAdvanced Elastomer Systems. Santoprene® 201-55 was blended withrespective crosslinked SBR masterbatches in the weight ratio 52.5:47.5.The dry blends were physically mixed, homogenized and injection moldedin an injection-molding machine to mold specimens. As a control,additional amount of polypropylene was added to Santoprene® 201-55 toincrease the hardness values for comparison to the molded specimens ofblends of Santoprene® 201-55 with crosslinked SBR masterbatches(Examples 11-13) that had higher amounts of polypropylene that was apart of the SBR masterbatches. The samples were prepared using aBattenfeld BA 800/315 injection-molding machine. The samples were moldedby using zone temperatures of Nozzle/Forward/Middle/Rear of205/199/199/193° C. respectively and an injection pressure of 20,000lbs/in².

TABLE 5 Composition in Weight % for Preparing Thermoplastic Vulcanizesfor TPE Containing Crosslinked EPDM and Crosslinked SBR 10+ 11 12 13Santoprene ® 201-55 84.8 52.5 52.5 52.5 Homopolymer Polypropylene 18.2 —— — (Atofina 3825, 30 Melt Flow Index) XL-SBR1 — 47.5 — — XL-SBR3 — —47.5 — XL-SBR4 — — — 47.5 Total 100 100 100 100 +Control

TABLE 6 Properties of TPE Containing Crosslinked EPDM and CrosslinkedSBR Prepared in Table 5 No 10+ 11 12 13 Shore A Hardness 82 84 82 85Tensile Strength 7.2 6.9 6 6.4 (Mpa) Tear Strength 32 23 27.4 27 (N/mm)Flexural Modulus 83 82 88 71 (Mpa) % Compression Set B @ 23 C. 24 2021.2 20 @ 70 C. 39.3 36.7 32.5 36 % Weight Gain IRM Oil 903 @ 70 C. 4436 42 43 % Force Retention* Time t = 0 hours 100 100 100 100 Time t = 24hours 74 89 73 84 Time t = 72 hours 59 84 72 64 +Control

Examples 11-13 that contained both crosslinked EPDM and crosslinked SBRhave the lowest compression set. This indicates the improvement in thesealing performance of the elastomer composition that is observed whencrosslinked SBR is present in thermoplastic vulcanizates that containcrosslinked EPDM. Low compression set is desirable for many seals. Also,the % Force retention in a stress relaxation experiment is very high forExamples 11, 12, and 13, indicating the ability of the crosslinked SBRwith proper selection of vinyl content, styrene content, coupling, andmolecular weight to maintain a high level of sealing force during thelife of a seal. Higher force retention is desired for the sealing.Particularly, Example 11 that contained a SnCl₄ coupled crosslinked SBRwith a high vinyl content and a high molecular weight has the highestlevel of sealing force maintained at the end of the test period.

The ratio of crosslinked SBR to crosslinked EPDM may be varied from20:80 to 80:20. It is possible to separately crosslink SBR and EPDM inpresence of an olefin resin and then blend them together for makingseals or molded parts. It is also possible to crosslink either SBR orEPDM simultaneously in one process step in presence of polyolefin resin,and processing oil.

The seals prepared with the thermoplastic elastomer containingcrosslinked solution diene rubber may be used in the construction,electrical, industrial, automotive, fluid delivery, dynamic seals, andappliances. Some examples of the applications are the seals forresidential windows, architectural windows, storefronts, entrances,atriums, skylights, roof windows, greenhouses, carports, sloped glazing,curtainwall and high-rises, glazing gaskets, glazing seals, rainscreens,secondary seals, primary seals, doorsweeps, door seals, rail pads, railboots, rail flanges, building, architectural, highway bridge andexpansion joints, geomembranes, bridge bearing pads, and architecturalbearing pads. Examples of some of the applications where thethermoplastic elastomer compositions can be used are; electricalconnectors, seals for electrical enclosures, grommets, gaskets, spliceseals, terminators, boots, plugs cables, jackets, wires, cord seals,grommets and gaskets for industrial equipment, food processingequipment, and manufacturing equipment may be used with thethermoplastic elastomer. In automotive, the belts, hoses, covers,sockets, mounts, dampers, weatherseals, doorseals, trunklid seals,windshield gaskets, static and dynamic seals, constant velocity joint(CVJ) boots, rack and pinion boots, miscellaneous automotive boots maybe prepared with the said thermoplastic elastomer. In fluid deliveryapplications, the thermoplastic elastomer containing crosslinked dieneelastomer may be used in pipe seals, pipe connectors, irrigationdelivery seals, culvert seals, and pipe couplings. For dynamicapplications, the cartwheels, castors, tires, boots, bellows, hoseconnectors may be prepared with the thermoplastic elastomer.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

1. A polymeric composition having excellent characteristics for utilization in manufacturing seals and gaskets including dimensional stability, low compression set and outstanding sealing characteristics, said polymeric composition being comprised of a blend of (A) a thermoplastic resin selected from the group consisting of polypropylene, polyethylene, poly phenylene ether, polystyrene, and styrene containing copolymer resins, (B) an elastomeric polymer selected from the group consisting of block copolymer comprising a first polymeric block that is comprised of repeat units that are derived from a vinyl aromatic monomer and a second block that is comprised of repeat units that are derived from a conjugated diolefin monomer, wherein the repeat units in the second block are hydrogenated, and wherein the repeat units in the second block are elastomeric in nature, and a crosslinked olefinic elastomer, (C) a high molecular weight crosslinked diene elastomer comprised of repeat units that are derived from conjugated diene monomer selected from the group consisting of 1,3-butadiene and isoprene, wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 200,000, and (D) an oil.
 2. A polymeric composition as specified in claim 1 wherein the thermoplastic resin is present at a level which is within the range of about 5 parts by weight to 60 parts by weight, wherein the elastomeric polymer is present at a level which is within the range of 5 parts by weight to about 90 parts by weight, wherein the high molecular weight crosslinked diene elastomer is present at a level which is within the range of about 5 parts by weight to about 90 parts by weight, and wherein the oil is present at a level which is within the range of about 15 parts by weight to about 600 parts by weight.
 3. A polymeric composition as specified in claim 2 wherein the high molecular weight crosslinked diene elastomer is dynamically crosslinked during a thermo-mechanical mixing step in the presence of the thermoplastic resin.
 4. A polymeric composition as specified in claim 2 wherein the thermoplastic resin is selected from the group consisting of polypropylene, polyethylene, polyphenylene ether, and polystyrene.
 5. A polymeric composition as specified in claim 2 wherein the thermoplastic resin is a styrene containing copolymer resin.
 6. A polymeric composition as specified in claim 2 wherein an elastomeric polymer is a block copolymer comprising a first polymeric block that is comprised of repeat units that are derived from a vinyl aromatic monomer and a second block that is comprised of repeat units that are derived from a conjugated diolefin monomer, wherein at least about 90% of the repeat units in the second block are hydrogenated.
 7. A polymeric composition as specified in claim 6 wherein the block copolymer is selected from the group consisting of styrene-ethylene, butylene-styrene block copolymers, styrene-ethylene, propylene-styrene block copolymers, styrene-ethylene, propylene block copolymers, styrene-ethylene, ethylene propylene-styrene block copolymers, partially hydrogenated products of styrene-isoprene, butadiene-styrene block copolymers, styrene-butadiene-styrene block copolymers, and styrene-isoprene-styrene block copolymers.
 8. A polymeric composition as specified in claim 6 wherein the block copolymer is a styrene-ethylene, butylene-styrene triblock polymer, wherein the ethylene, butylene block is obtained by the hydrogenation of a butadiene mid block with a vinyl content of no less than 30 percent by weight.
 9. A polymeric composition as specified in claim 6 wherein the block copolymer has a weight average molecular weight of at least 100,000.
 10. A polymeric composition as specified in claim 6 wherein the block copolymer has a weight average molecular weight of at least 150,000.
 11. A polymeric composition as specified in claim 2 wherein the a high molecular weight crosslinked diene elastomer is a styrene-butadiene rubber having a bound styrene content that is within the range of 5% to 40% by weight and a vinyl content that is within the range of about 5% to 80% by weight, and wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 275,000.
 12. A polymeric composition as specified in claim 2 wherein the a high molecular weight crosslinked diene elastomer is comprised of repeat units that are derived from 1,3-butadiene, isoprene, and optionally, a vinyl aromatic monomer, wherein the repeat units in the crosslinkable elastomer are distributed in a random manner, wherein the crosslinkable elastomer is coupled with a tin (Sn) coupling agent or a silicon (Si) coupling agent, and wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 275,000.
 13. A polymeric composition as specified in claim 2 wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 375,000.
 14. A polymeric composition as specified in claim 2 wherein the high molecular weight diene elastomer is selected from the group consisting of nitrile rubbers and hydrogenated nitrile rubbers.
 15. A polymeric composition as specified in claim 2 wherein the elastomeric polymer is a crosslinked olefinic elastomer wherein the olefin elastomer is a polyolefin copolymeric elastomer having repeat units that are derived from at least 2 members selected from the group consisting of ethylene, propylene, butene, hexene, and octane, arid wherein the crosslinked olefinic elastomer has a Mooney ML 1+4 viscosity at 125° C. of at least about
 45. 16. A polymeric composition as specified in claim 15 wherein the polyolefin copolymer elastomer is an ethylene-propylene-diene elastomer.
 17. A polymeric composition as specified in claim 2 wherein the oil is an extender oil selected from the group consisting of paraffinic oils, naphthenic oils, and polybutene.
 18. A process for making a polymeric composition having excellent characteristics for seals and gaskets including dimensional stability, low compression set and outstanding sealing characteristics, said process comprising dynamically vulcanizing a blend of (A) a thermoplastic resin selected from the group consisting of polypropylene, polyethylene, poly phenylene ether, polystyrene, and styrene containing copolymer resins, (B) an elastomeric polymer selected from the group consisting of block copolymer comprising a first polymeric block that is comprised of repeat units that are derived from a vinyl aromatic monomer and a second block that is comprised of repeat units that are derived from a conjugated diolefin monomer, wherein the repeat units in the second block are hydrogenated, and wherein the repeat units in the second block are elastomeric in nature, and an olefinic elastomer, (C) a high molecular weight diene elastomer comprised of repeat units that are derived from conjugated diene monomer selected from the group consisting of 1,3-butadiene and isoprene, wherein the high molecular weight diene elastomer has a weight average molecular weight of at least about 200,000, and (D) an oil.
 19. A process as specified in claim 18 wherein the thermoplastic resin is present at a level which is within the range of about 5 parts by weight to 60 parts by weight, wherein the elastomeric polymer is present at a level which is within the range of 5 parts by weight to about 90 parts by weight, wherein the high molecular weight crosslinked diene elastomer is present at a level which is within the range of about 5 parts by weight to about 90 parts by weight, and wherein the oil is present at a level which is within the range of about 15 parts by weight to about 600 parts by weight.
 20. A process as specified in claim 19 wherein the thermoplastic resin is selected from the group consisting of polypropylene, polyethylene, polyphenylene ether, and polystyrene. 